This invention relates to a device used in a wood sawing machine for supporting a circular saw that works below the work, particularly to a supporting device which can raise or lower the circular saw corresponding to the requirements for operating different workpieces and regulate the tension of a transmission belt that transmits power from a motor to the circular saw.
Various forms of circular sawing machines have existed in the arts. In some circular sawing machines, the circular saws are mounted to the lower arbors which can be raised or lowered to adjust the positions of the circular saws for matching the operations for various works. In a typical circular sawing machine which is shown in FIGS. 1a and 1b, a circular saw 10 is mounted on a lower arbor disposed in a sleeve 11 which is mounted on a support 12 having its arms 12a and 12b pivoted, about horizontal pivot axes 13c, to two brackets 13a and 13b. The horizontal portion of the support 12 is connected to a hydraulic piston rod 16 and the circular saw 10 is driven by a motor 15 through a transmission belt 14. The circular saw 10 can be adjusted in its height relative to the worktable by the action of the piston rod 16 which causes the support 12 to turn about the horizontal pivot axes 13c. However, such a machine has a disadvantage in that, when the tension of the transmission belt 14 is required to be adjusted, the position of the motor 15 must be changed in the direction as shown by arrow A. As the motor's position is changed, the axis of the rotation of the support 12 and the axis of the power output shaft can not be in an alignment. This results in that the angular displacement of the support 12 about the pivot axes 13c for adjusting the position of the circular saw 10 undesirably affects the tension of the belt, ie, the tension of the belt may be exceedingly high or low. If the axes of the motor and the arbor are not made parallel after changing the position of the motor, it will result in an improper alignment of the belt and pulleys which may cause the operation of the circular saw imperfect.